1. Field of the Invention
The present invention relates to a cylinder cooling apparatus for an air-cooled engine, wherein cooling air from a cooling fan cools the cylinder of the engine.
2. Description of the Related Art
As disclosed, for example, in Japanese Patent Application Laid-Open Publication No. Hei 10-227254 (Conventional technology 1), Japanese Patent Application Laid-Open Publication No. Hei 06-42347 (Conventional technology 2), and Japanese Patent Application Laid-Open Publication No. Hei 07-293238 (Conventional technology 3), various proposals are made in which a cooling air passage for guiding the cooling air from a cooling fan to a cylinder and a cylinder head is formed into an appropriate shape so that a cylinder and a cylinder head being high in temperature are cooled uniformly as much as possible.
Furthermore, a cylinder-inclined overhead valve engine in which its cylinder is inclined so that the total height of the engine is suppressed low is disclosed in Patent document 4. In this cylinder-inclined overhead valve engine, the cams on a camshaft disposed below the cylinder rock the rocker arms disposed above the cylinder via tappets and pushrods, whereby the air intake and exhaust valves disposed in the cylinder head are moved up and down. The tappets and the pushrods are disposed on the lower side of the inclined cylinder. When the inclined cylinder is viewed from the crankshaft of the engine, only a cylinder outer circumferential wall section is present on the upper side of the inclined cylinder. Hence, the thickness of the cylinder outer circumferential wall section on the upper side is not particularly large. On the other hand, the pushrods, etc. are present on the lower side of the inclined cylinder. Hence, the thickness of the cylinder outer circumferential wall section on the lower side is large. For this reason, when the inclined cylinder is viewed from the crankshaft of the engine, the configuration of the cylinder and the thickness of the cylinder outer circumferential wall section on the upper side are greatly different from those on the lower side.